In certain areas of the world prone to extreme weather conditions, such as hurricanes, typhoons, earthquakes, tornadoes, etc., contractors are often required to adhere to strict regional building codes established to ensure buildings are constructed to withstand these intense conditions.
The roof of a building is the uppermost structural assembly and particularly vulnerable to these adverse conditions, (e.g., high wind shear generated during a hurricane or tornado). The roof is supported by exterior and/or interior support walls and can have many shapes and geometries; the most common roof structures consist of trusses or rafters, or I-beams made of wood, steel, etc. During high wind shear, the roof can act like a low efficiency wind foil creating vertical uplift or lateral thrust forces on the windward and leeward side of the roof. These forces can create stress that may lift off the top of the building. If the roof fails, these winds can enter the building causing greater destruction.
The manner in which the structural members (e.g., trusses, rafters, beams, joists) are connected to the support members (e.g., walls) of a building has received much regulation as these areas are the most likely to fail during the application of loads other than gravitational, such as uplift or lateral thrust forces. When properly secured together the loads experienced by the structural members distribute the upward lift and lateral thrust along the support member to the foundation. Thus, these loads are countervailed by the overall weight of the building.
In masonry construction, a key structural element of the support wall is the tie-beam or bond-beam, often fortified internally with reinforcement bars. The tie-beam, bond-beam, or other support structure is located at the top of the wall and used to attach the structural members. The beam can either be poured concrete (i.e., U-shaped concrete or forms filled with concrete) or pre-constructed masonry bond beams.
In wood-frame construction, the support walls are usually framed with 2″×4″, 2″×6″, or 2″×8″ or other structural-grade lumber or materials. The support walls consist of a sole plate located at the bottom, studs (typically spaced at 16″ on center), and a double top plate on which the structural members are mounted.
Numerous anchoring devices have been designed for securing structural members to the various support members, some of which include: angles, straps, holdowns, pre-deflected holdowns, tension ties coiled strapping, rafter ties, truss anchors, truss straps, strap truss tie down, masonry uplift connectors, girder tie down, uplift girder ties, wind/seismic anchors. The appropriate anchoring system depends upon the type of construction (wood, masonry, metal, etc.), type of roof (truss, rafter, girder or other).
Each of these aforementioned anchoring systems have their own fastening features, that is, different sizes of nails, screws, bolts, slant nailing via dimple nail holes, diamond holes, speed prongs, slot holes, and other special hardware. The licensed professional engineer must perform load and stress analysis at each point where the structural member and support member meet (i.e., bearing point), this requires the specification of beams sizes, reinforcement and anchor system used, type and number of fasteners used, etc. This process is time consuming and creates increased costs and delays in building construction.
In masonry construction, when the tie-beams are cast, a portion of the anchoring device is placed within the wet concrete. Next, the structural members are mounted onto the tie-beams. One problem that frequently occurs is that the structural members (e.g., truss/rafter) end up positioned away from where the anchoring devices are permanently attached to the concrete. In such instances, different anchors designed for retrofit applications must be installed in juxtaposed relation to each structural member. This retrofit process requires drilling into the tie-beam after the concrete has adequately hardened for placement of wedge bolts or threaded rods that will need to be epoxied in place and subsequently undergo a curing period before fastening the anchors to the structural members, thereby, possibly delaying construction and increasing cost.
Wood structural members present an additional problem as these anchors are often fastened to structural members using nails that can cause the wood to split since most of these members are made of southern pine lumber, which has a high strength but tends to split easily. This can undermine the integrity and strength of the structural member.
What has been heretofore lacking in the art is a universal, removable anchoring system of (1) adequate strength for utilization in all types of construction (masonry, metal, wood, etc.) using standard hardware (bolts, nuts, etc.), (2) having infinite adjustability whereby location of the structural members prior to installation is not needed, and (3) designed for maximum strength under load in a surface-mounted orientation.